It has long been desirable to prepare .beta.-phenylethyl alcohol in a low cost process. This material is a valuable intermediate in the preparation of fragrances and of styrene, a commercial chemical with widely varying uses. In the past, it has been proposed that .beta.-phenylethyl alcohol be prepared from benzyl alcohol. For example, the reaction has been described by Wender, I. et al., J. Am. Chem. Soc. 71 (1949), pages 4160-4161 in the presence of a cobalt catalyst. This early work is summarized by Orchin in Advances in Catalysis, Vol. V (1953), pages 393-414. This author reports that, at 185.degree. C., a 50-60% yield of toluene and a 25-35% yield of .beta.-phenylethanol is obtained. Other workers have experimented with this reaction, particularly Y. B. Kryukov et al., Neftekhimiya, 1970, 10 (1), at page 83. Here, a vapor phase reaction is described over an iron, alumina, vanadium and potassium catalyst at 450.degree. C. and 50 atmospheres pressure. Unfortunately, in this latter reaction extremely low selectivities to the .beta.-phenylethanol were obtained.
Though not related to the formation of .beta.-phenylethanol, homologation has been described by a series of patents assigned to Commercial Solvents, including U.S. Pat. Nos. 3,248,432 and 3,285,948, British Pat. No. 951,506, and Belgian Pat. Nos. 618,413 and 625,939. These references are primarily concerned with the homologation of methanol to form ethanol. The catalyst system shown in the U.S. Pat. No. 3,285,948 is of particular interest. This patent discloses the use of a cobalt catalyst promoted with a ruthenium or osmium halide and iodine. The patent also discloses the optional use of from 0.1 to 20% of water based on the methanol charged in the reaction system. Reaction temperatures indicated are 175.degree. to 230.degree. C., preferably from 190.degree. to 210.degree. C.
Unfortunately, the foregoing references fail to result in the preparation of high yields of .beta.-phenylethanol. The work reported by Orchin forms so little .beta.-phenylethanol that such reaction could not be considered of commercial importance. On the other hand, the work by Commercial Solvents on methyl alcohol does not suggest the homologation of benzyl alcohol.
The process of the present invention, which is distinguishable from the foregoing prior art, surprisingly yields high selectivity to the desired .beta.-phenylethanol. Selectivities of over 60% are obtained, in certain instances, up to 80%. This is over twice the selectivity to .beta.-phenylethanol reported in the prior art. This surprising improvement results from performing the process in the presence of a promoted cobalt catalyst and at least some water at a temperature substantially lower than that taught in the prior art, namely, from 100.degree. to 165.degree. C. Further improvements are obtained by using selected hydrogen to carbon monoxide ratios and even more specific temperatures.